We have demonstrated that PKC zeta can inhibit invasion and metastasis of Dunning rat prostate cancer cells and that 12-0-tetradecanoylphorbol-13 acetate (TPA)-induced apoptosis of LNCaP human prostate cancer cells is due to prolonged activation of one or more PKC isozymes. The overall aims of this project are to elucidate mechanisms underlying those phenomena, with an emphasis on defining new therapeutic targets.
The specific aims are: 1) To test the hypothesis that a) PKC zeta-directed suppression of Matrigel digesting and metastatic abilities of MAT-LyLu cells is due to increase activity of metalloproteinases (MMPs) or increased activity of tissue inhibitors of metalloproteinases (TIMPs), b) over-expression of PKC zeta causes changes in expression of genes coding for proteins that regulate metastasis and, c) PKC zeta binding protein Par-4 abrogates the ability of PKC zeta to inhibit metastasis. Those studies will be performed using zymography/immunoblotting, differential display-PCR, and migration of MAT-LyLu transfectants through Matrigel, respectively. 2) We will determine PKC isozyme specificity of TPA-induced apoptosis of LNCaP and evaluate abilities of less toxic PKC activators to induce LNCaP apoptosis. Those studies will utilize inducible over-expression and inhibition of individual PKC isozymes and the effects of bryostatins 1 and 2 on LNCaP cells. 3) We will clarify dependence of PKC-induced LNCaP apoptosis on enzymes of the MAP kinase pathway and differences in that pathway between LNCaP, TPA-resistant prostate cancer cell lines and cells that are stimulated to grow by TPA. Those studies will include gel retardation assays to compare in those cell type proteins bound to MAP PKC-mediated metastasis suppression and apoptosis should help determine under what circumstances inhibition or activation of PKC is warranted, and whether certain isozymes are better targets for activation and other for inhibition in prostate cancer. That may lead to more specific targets in the treatment of cancer.
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